CD4 and viral infectious disease: Excessive IL-22 significantly reduced the number of viral-specific IFN-γ+TNF-α+ CD4+ and CD8+ T cells in the spleen and liver (Fig. 6D) and also resulted in a lower proportion of cytokine-producing T cells in the spleen (Supplementary Fig. S3C), indicating that IL-22 dampened production of multi-functional T cells in acute viral infection.